“Computers only know ones and zeros!” If your child has come home with that news, they’ve met binary. It sounds like something for high school, but the big idea is simple enough for a seven-year-old: a light is on or off, an answer is yes or no. Here’s binary for kids in plain words, why computers use it, a binary card game you can make from scrap card, pixel pictures, secret binary messages, and what children learn about data at school.
What is binary?
Binary is a way of writing information with just two symbols. CS Unplugged, the free computer science project from the University of Canterbury in New Zealand, puts it like this: “The simplest and most common way to represent digits is the binary number system, with just two digits (usually written as 0 and 1).” It’s called binary “because there are only two different digits used, or two states.”
Each 0 or 1 is called a bit, short for binary digit. CS Unplugged has a fun way to show the name: write “binary digit” on paper, tear off the “bi” at the start and the “t” at the end, and put them together.
Why do computers use 1s and 0s?
Inside a computer are billions of tiny parts that, in CS Unplugged’s words for young children, “can be turned on or off, like a light switch”. A bit is stored in a circuit that is set to “a high voltage level (1) or a low voltage level (0)”. Those billions of bits store “text, numbers, images, video, and anything else that we need to store or transmit”.
Why only two? “Computers are cheaper and easier to build if they represent data with just two contrasting values, which we represent as the numbers 0 and 1.” There aren’t really tiny 0s and 1s zooming around inside. The 1 and 0 are just names for two states, the way “on” and “off” are.
On and off, yes and no: same idea, different symbols
This is the part young children grasp quickly. Any two opposites can do the job of 1 and 0. CS Unplugged suggests cards held up high or down low, sitting down or standing up, lights on or off, “a cross or tick; happy or sad face”. KidStudy’s lesson shows the same yes in many ways: the word yes, a tick, a thumbs up, a green light, or a one.
Try a quick sort at home. Walk around and decide: is the torch on or off? The TV? The fridge light when the door is closed? Call on “one” and off “zero”, and you’re already speaking binary.
The binary card game
This is CS Unplugged’s first binary lesson, and the Australian Government’s Digital Technologies Hub uses it as its example of teaching without a computer. You need four pieces of card and a texta.
- Make the cards. Draw 1 dot on the first card, 2 on the next, then 4, then 8. Ask your child to guess each card before you draw it. Children often guess 3 after the 2, and 6 after the 4, before they notice that each card doubles.
- Line them up from biggest to smallest: 8, 4, 2, 1. The smallest card goes on the right, just like the ones place in ordinary numbers.
- Learn the rule. A card is either face up, showing its dots (that’s a 1), or face down (that’s a 0). Nothing in between.
- Make 3. Start with the biggest card. Does 8 fit into 3? No, so flip it down. Does 4 fit? No, flip it down. Does 2 fit? Yes, keep it up, with 1 left over. The 1 card stays up. That’s 0011.
- Count up from 0. All cards down is 0. Then count 1, 2, 3 and keep going until every card is up, which makes 15. Watch the 1 card: it flips every time.
- Add a 16 card when your child is ready. With five cards you can count all the way to 31.
| Number | 8 | 4 | 2 | 1 | Binary |
|---|---|---|---|---|---|
| 0 | down | down | down | down | 0000 |
| 3 | down | down | up | up | 0011 |
| 8 | up | down | down | down | 1000 |
| 9 | up | down | down | up | 1001 |
| 15 | up | up | up | up | 1111 |
Pixel pictures: how a picture becomes 1s and 0s
A screen picture is made of tiny squares called pixels. CS Unplugged explains that “computer images are ultimately represented inside a computer using just 0’s and 1’s.” Your child can see this with grid paper.
- Draw a grid five squares wide and five squares tall.
- Read out a code for each row. Your child colours a square for each one and leaves it white for each zero.
- Try this heart, from KidStudy’s lesson: 01010, 11111, 11111, 01110, 00100.
- Swap jobs: your child designs a picture, writes its code and reads it to you.
Send a secret binary message
Once your child can make numbers, letters are easy. Use 1 for A, 2 for B, and so on. In CS Unplugged’s version, you say “No, Yes, No, No, No” for five cards (16, 8, 4, 2, 1). That’s 8, the letter H. Then “No, Yes, No, No, Yes” is 9, the letter I. The message is “HI”. You can also say on and off, or up and down. For more ways to hide a message, see our post on secret codes for kids.
KidStudy’s lesson goes further back: long ago, ships far apart sent messages with flashing lamps, where short and long flashes stood for letters. Today, computers send ones and zeros through wires and through the air.
What children learn at school
Showing the same information in different ways is part of Digital Technologies from the first years of school. Binary itself comes by name in Years 5 and 6.
- In Victoria, at Levels 3 and 4, children “recognise different types of data and explore how the same data can be represented differently depending on the purpose” (VC2TDI4D01), with the example of “four, 4, IV, |||| and quatre”. They also “explore transmitting different types of data between digital systems” (VC2TDI4S02). At Levels 5 and 6, they “explore how data can be represented using binary” (VC2TDI6D01), including “demonstrating that an on/off state in a circuit can represent the digits 1 and 0”.
- In the Australian Curriculum, Years 3 and 4 have the same data description (AC9TDI4K03), and Years 5 and 6 “explore how data can be represented by off and on states (zeros and ones in binary)” (AC9TDI6K04).
KidStudy’s Year 3 Coding lesson, On and Off, covers two-symbol data: sorting things that are on or off, reading a pixel code where one is black and zero is white, showing yes in different ways, and how computers send pictures, words and sounds as ones and zeros. Its 10-minute home activity, Pixel picture, is the grid game above. If your child enjoys this, the screen-free games in our post on unplugged coding activities make a good next step.
Questions parents ask
What is binary in simple terms?
Binary is a way of writing information using only two symbols, usually 1 and 0. You can think of them as on and off, or yes and no. Computers use binary to store everything, from numbers and words to pictures and music.
Why do computers use binary?
A computer’s tiny parts are set to one of two states, a high or low voltage, which we call 1 and 0. CS Unplugged explains that computers are cheaper and easier to build with just two contrasting values.
What is a bit?
A bit is one binary digit, a single 1 or 0. Eight bits together make a byte.
How do you teach binary to kids?
Make four cards with 1, 2, 4 and 8 dots. Each card is either face up (1) or face down (0). Ask your child to make numbers by choosing which cards to show, starting with the biggest card.
What year do kids learn binary in Australia?
Binary is named in the curriculum in Years 5 and 6, in both the Victorian and Australian curriculums. In Years 3 and 4, children explore how the same data can be shown in different ways, which is the idea behind it.
Is binary maths or coding?
Both. It’s a number system, so it builds counting and doubling skills, and it’s how computers store data, which is part of Digital Technologies.
Sources
- Binary numbers, CS Unplugged, University of Canterbury
- How binary digits work (ages 5 to 7) and (ages 8 to 10), CS Unplugged
- Codes for letters using binary representation, CS Unplugged
- Image representation, CS Unplugged
- Teaching unplugged, Digital Technologies Hub, Australian Government Department of Education
- Victorian Curriculum F–10 Version 2.0: Digital Technologies, VCAA
- Years 3–4 and Years 5–6: Digital Technologies (Australian Curriculum v9.0), Queensland Curriculum and Assessment Authority
